Highly heat-resistant metallic carrier for an automobile catalyst

ABSTRACT

A metallic carrier for an automobile catalyst, comprising a metallic honeycomb and a jacket, characterized in that a foil material constituting the metallic honeycomb is comprised of an Fe-Cr-Al-base alloy and has high-temperature proof stresses of 22 kgf/mm 2  or more and 11 kgf/mm 2  or more respectively at 600° C. and 700° C. with the foil material as annealed at a temperature of the recrystallization temperature of the foil material or above.

TECHNICAL FIELD

The present invention relates to a highly heat-resistant metalliccarrier for an automobile catalyst, that can cope with an increase inthe temperature of an automobile engine exhaust gas.

BACKGROUND ART

A ceramic honeycomb composed mainly of cordierite has hitherto been usedextensively as a carrier for a catalyst for rendering an automobileexhaust pollution-free. In recent years, the advantages of a metallichoneycomb comprising a stainless steel foil have been recognized, andthe metallic honeycomb has begun to be mounted on some high gradepassenger cars, which has led to an increasing tendency that the numberof the metallic honeycombs installed in automobiles has graduallyincreased. The advantages of the metallic honeycomb include thefollowing: 1 since the temperature rise rate at the start of an engineis higher than that in the case of the ceramic honeycomb, the metallichoneycomb can begin to exhibit catalytic activity for purifying theexhaust gas earlier than the ceramic honeycomb, which contributes to areduction in the amount of release of toxic gases; 2 since the wallthickness is half or smaller than that of the ceramic honeycomb, theexhaustion resistance becomes so small that the output loss of theengine is small; 3 the surface area per unit volume of the honeycomb isso large that it is possible to relatively reduce the size; and 4 in theceramic honeycomb, a cushioning material comprising a wire of inconel ora high grade stainless steel should be interposed between the honeycomband the jacket and, due to poor heat resistance of the cushioningmaterial, there is a limitation on an increase in the temperature of theexhaust gas, whereas the metallic honeycomb is directly joined to thejacket, so that no cushioning material is needed and it can be disposedat a higher temperature portion immediately behind the engine manifoldto shorten the build up time of the purification activity of thecatalyst.

The metallic honeycomb can be used at a higher temperature than theceramic honeycomb. In recent years, however, there is an ever-increasingdemand for lean burn and high speed running with low fuel consumptionagainst the background of tightening of CAFE and regulation of exhaustgases, which has lead to a tendency of a further increase in thetemperature of the exhaust gas from an automobile engine, so that, insome cases, the conventional metallic honeycombs cannot satisfy the newheat resistance requirements.

Specifically, the inlet gas temperature to which the conventionalmetallic honeycombs have been exposed was about 850° C. at the highesteven when they were used immediately behind the engine manifold. Inrecent years, however, the inlet gas temperature often reaches 900° to1,000° C. This has made it impossible for the conventional metallichoneycombs to pass a strict test for durability requirements.

For example, as described on pages 70 to 80 of "Nikkei Mekanikaru(Nikkei Mechanical)", No. 20 issued on January in 1992, an improvementin the oxidation resistance of the honeycomb has been considered as thefirst requirement to be satisfied for improving the heat resistance ofthe metallic honeycomb. For this reason, as disclosed in, for example,Japanese Unexamined Patent Publication (Kokai) Nos. 92286/1975,48473/1976 and 71898/1982, attention has been directed to the oxidationresistance of a foil material for a metallic honeycomb and the adhesionof a film, and use has been made of a foil comprising, as a basematerial, an Fe-Cr-Al-base alloy, which has hitherto been extensivelyused as a heating wire and a high-temperature member for heaters byvirtue of its excellent oxidation resistance and adhesion as a film, andhaving improved heat resistance or adhesion to an activated alumina(y-Al₂ O₃) coated layer serving directly as a carrier for the catalyst.In all the techniques disclosed in the above-described publications, Yis utilized as means for improving the oxidation resistance of thematerial.

On the other hand, Japanese Examined Patent Publication (Kokoku) No.2-58340 proposes an Fe-Cr-Al-base alloy containing 0.06% by weight intotal of rare earth elements including 0.002 to 0.05% by weight of arare earth element selected from La, Ce, Pr and Nd added mainly for thepurpose of preventing peeling of an oxide film of the alloy and anFe-Cr-Al-base alloy containing Zr for the purpose of stabilizing thealloy and Nb in an amount enough to satisfy a particular relationshipthereof with the C content and N content for the purpose of ensuring thehigh-temperature creep strength. In these publications, there is adescription to the effect that, when the total content of the rare earthelements exceeds 0.06% by weight, no significant improvement in theoxidation resistance can be attained as compared with a total content of0.06% by weight or less and, further, it becomes impossible to effectworking at conventional hot working temperatures.

Similarly, Japanese Unexamined Patent Publication (Kokai) No. 63-45351proposes an Fe-Cr-Al-base alloy wherein the above-described rare earthelement exclusive of Ce or La alone are added in an amount in the rangeof from 0.05 to 0.2% by weight because the addition of Y increases theproduction cost. According to the description of the publication, theproposal is based on a finding that the presence of Ce is causative of alowering in the hot workability attributable to the addition of theabove-described rare earth elements and also deteriorates the oxidationresistance and the addition of the rare earth elements exclusive of Cealone renders the material hot-workable and further contributes to animprovement in the oxidation resistance. However, the rare earthelements are very reactive and similar to one another in the chemicalproperties, so that the separation of individual rare earth elements isnot easy, which renders the separated rare earth elements very expensiveas compared with a mischmetal comprising a conventional mixture of rareearth elements. For this reason, as with the sole use of La, theseparation and removal of Ce alone inevitably incurs an increase in thecost. Further, Japanese Unexamined Patent Publication (Kokai) No.63-42356 of which the applicant is the same as that of theabove-described Japanese Unexamined Patent Publication (Kokai) No.63-45351 discloses an Fe-Cr-Al-base alloy which is excellent inoxidation resistance and peeling resistance of oxide scale and contains0.01 to 0.30% in total of Ce, La, Pr and Nd. In this publication,however, no study has been made on the hot workability of the alloy.

In the above-described prior art, although the adhesion and oxidationresistance of an oxide film have been studied with a view to improvingthe heat resistance of the metallic carrier, the influence of the foilmaterial on the durability of the honeycomb structure, for example,high-temperature proof stress, which is a very important necessaryproperty for a foil constituting a honeycomb of the catalyst from thepractical point of view, has not been studied at all.

The present invention has been made with a view to solving the problemof lack of heat resistance of the conventional metallic carrierassociated with an increase in the temperature of automobile engineexhaust, and an object of the present invention is to provide a highlyheat resistant metallic carrier capable of withstanding engine exhausthaving a higher temperature (900° to 1,000° C.).

CONSTRUCTION OF INVENTION

In order to attain the above-described object, the metallic carrier fora catalyst according to the present invention comprises a honeycomb anda jacket, wherein the honeycomb comprises a foil material comprising anFe-Cr-Al-base alloy and having high-temperature proof stresses of 22kgf/mm² or more and 11 kgf/mm² or more at 600° C. and 700° C.respectively, the foil material being annealed at a temperature of therecrystallization temperature of the foil material or above.

Further, chemical ingredients constituting the foil material have beenspecified as one means for attaining the above-describedhigh-temperature proof stress.

Specifically, precipitation strengthening or solid-solutionstrengthening elements, such as Ta, Nb, Mo and W, are added in a givenamount to the foil material for the purpose of enhancing the proofstress of the foil material in the temperature range of from 600° to700° C. In fact, experiments conducted by the present inventors haverevealed that the metallic carrier comprising the above-described foilmaterial having a high proof stress can withstand an engine benchthermal shock durability test wherein the maximum temperature is 950° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the relationship between the distance from ajacket to the center of a carrier of a honeycomb body and thetemperature (curve 1) and the relationship between the number of pliesof the carrier and the shearing strain of a corrugated sheet of ahoneycomb body (curves 2 and 3), wherein curve 2 is for a conventionalexample and curve 3 is for an example of the present invention;

FIG. 2 is a diagram showing the relationship between the temperature ofa honeycomb body and the high-temperature proof stresses of aconventional example (curve 4) and an example of the present invention(curve 5);

FIG. 3 is a diagram showing the relationship between the amount of Nbadded and the proof stress;

FIG. 4 is a diagram showing the relationship between the amount of Moadded and the proof stress when Nb is added in combination with Mo; and

FIG. 5 is a perspective view of an embodiment of the structure of ametallic carrier.

BEST MODE FOR CARRYING OUR THE INVENTION

The best mode for carrying out the invention will now be described indetail.

In order to prepare the above-described metallic honeycomb capable ofwithstanding a high inlet gas temperature of 900° to 1000° C., thepresent inventors first conducted the following engine bench durabilitytest of a metallic carrier.

Specifically, a metallic carrier as shown in FIG. 5, which comprises ametallic honeycomb (20Cr-5Al-0.05Ti-0.08REM) having a diameter of 75 mmand a length of 100 mm and comprising a corrugated foil and flat foiland a jacket surrounding the outside of the metallic honeycomb, was usedas an example of the metallic carrier structure and subjected to athermal shock test wherein increasing of the temperature from 150° C. to950° C. followed by decreasing of the temperature from 950° C. to 150°C. (the maximum temperature being 100° C. above that of the conventionaltest) is repeated 1,200 times.

As a result, it has been found that even a metallic carrier, which canwithstand the conventional thermal shock test with the maximumtemperature being 850° C., is broken under the above-described newconditions. The broken site was several mm inside the outermostperiphery, and the base material portion of the corrugated plate removedfrom the joint of foils constituting the honeycomb was broken in thedirection of flow of exhaust, which caused the inner honeycomb to bedeviated in the direction of flow of exhaust. The qualitative reason forthe breaking is that, in the stage of rapidly increasing and decreasingthe temperature, there is a period of time that a temperature differenceof 400° C. or more occurs between the jacket of a thin stainless steelsheet for holding the honeycomb and the honeycomb, and, at that time, athermal strain caused by this temperature difference becomes largeenough to remarkably penetrate into a plastic region beyond the elasticlimit, so that the rise and fall of the thermal strain induce thermalfatigue failure of the honeycomb.

In the heat cycle of the metallic carrier, heating gives rise to a rapidincrease in the internal temperature of the honeycomb, while thetemperature rise rate of the jacket is low during the heating. Thiscauses a temperature difference between the jacket and the interior ofthe honeycomb, and the temperature difference is rapidly expanded.However, after a while, since the jacket also becomes heated, thetemperature difference is reduced, and a further reduction in thetemperature difference is observed in the stage of cooling. Therefore, aperiod of time that the temperature difference between the jacket andthe honeycomb is a maximum (400° C. or more) exists during each heatcycle.

The present inventors have analyzed the distribution of a shearingstrain attributable to a heterogeneous temperature distribution when themaximum temperature difference has occurred between the jacket and thehoneycomb by using a simplified thermoelastic-plastic model on thepremise that use is made of the above-described metallic carrier. As aresult, they have found that a rise and fall of a maximum thermal strainof about 0.7% or more occurs for each heat cycle in the honeycomb at itsportion where a failure occurs in the above-described engine bench test.

The results are shown in FIG. 1. In the drawing, curve 1 is obtained byeffecting the above-described test with the metallic carrier mountedimmediately behind an exhaust manifold to determine the temperaturedistribution at individual sites in the honeycomb from the jackettowards the center of the honeycomb and selecting a temperature curve inthe case of the maximum temperature difference between the jacket andthe honeycomb among the temperature curves for the respective heatcycles. The maximum temperature occurs when the site close to the centerof the honeycomb is heated to about 700° C. In this case, a sharptemperature gradient (temperature difference between the honeycomb andthe jacket: 400° C. or above) occurs in the honeycomb at a portion about15 mm from the jacket.

Curve 2 represents the distribution of a shearing strain measured usingthe above-described thermoelastic-plastic model, wherein the shearingstrain becomes maximum at a site having a sharp temperature gradientwhere there occurs a temperature change of 600° to 700° C. Although thesharpest temperature gradient is observed at temperatures of 600° C. orbelow, since the strength of the material increases with a lowering inthe temperature, the shearing strain is lower than that in theabove-described temperature range. Such a phenomenon is attributable toa change in the proof stress of the honeycomb material.

The present inventors have made studies on a change in 0.2% of proofstress with the temperature of the material and, as a result, have foundthat the proof stress of the material is rapidly lowered over thetemperature range of 600° to 700° C. This is shown in curve 4 of FIG. 2.

Specifically, it has been found that a region where the temperaturereaches 600° to 700° C. and gives rise to a rapid lowering in the proofstress of the material exists adjacent to a portion extending from ajacket 1 towards the outer periphery of a honeycomb 4 shown in FIG. 5and having the sharpest temperature gradient, and a large shearingstrain concentrates on this region.

In the metallic honeycomb, since a honeycomb is generally brazeddirectly to a jacket of a thin stainless steel sheet (thickness: 1.0 to2 mm), a temperature difference between the jacket and the honeycombcauses a large part of the thermal strain to be applied to the honeycombformed of a foil having a thickness (usually about 50 μm) much smallerthan the outer casting material. Further, a temperature distributionexists also within the honeycomb, and the proof stress of the materialvarys depending upon the temperature distribution, so that the thermalstrain concentrates on a region close to a portion having a sharptemperature gradient and the region having a relatively low proof stressof the material.

Thus, the present inventors have found that an improvement in the proofstress of the material at its portion in a temperature region where thehigh-temperature proof stress is rapidly lowered is very useful not onlyfor reducing the thermal strain but also for improving the durability ofthe carrier.

Based on this finding, the present inventors have prepared a hypotheticstrength profile (curve 5 of FIG. 2) wherein the proof stresses at 600°C. and 700° C. indicated by curve 4 of FIG. 2 each have been increasedby 50%, and determined the thermal strain distribution using theabove-described thermoelastic-plastic model. As a result, it has beenfound that, as shown in curve 3 of FIG. 1, the maximum percentageshearing strain became 0.25% which was much lower than that in curve 2of the same drawing.

Further, based on the above-described studies, the present inventorshave also made studies on the optimum high-temperature proof stress inthe temperature range in which a sharp temperature gradient is formed.As a result, they have found that, in order to maintain the durabilityof the metallic honeycomb where the inlet exhaust gas temperaturereaches a high temperature region of 900° C. or above, it is very usefulto bring the proof stresses at 600° C. and 700° C. of a foil comprisinga ferritic stainless steel containing Al to 22 kgf/mm² or more and 11kgf/mm² or more respectively with the foil annealed at a temperature atthe recrystallization temperature of the foil or above.

The reason why the heat resisting stainless steel foil material for thehoneycomb material in the metallic carrier is specified by thehigh-temperature proof stress (a value experimentally found as a yieldstress) will now be described.

Since the metallic carrier is subjected to a rapid heating-coolingcycle, the thermal fatigue resistance becomes a problem to be solved forimproving the heat resistance. The thermal fatigue resistance greatlydepends upon the high-temperature proof stress in the tensile test. Thatis, enhancing the proof stress corresponding to the yield stress must beaccomplished to improving the thermal fatigue resistance, and it ismeaningless to specify the foil material by the tensile strength whenthe thermal strain has greatly penetrated into a plastic region.

Further, the creep strength does not relate directly to the thermalfatigue resistance of the metallic carrier. For this reason, in thepresent invention, the foil material is specified by thehigh-temperature proof stress.

The reason why the proof stress is specified with the foil as annealedat a temperature of the recrystallization temperature of the foil orabove (900° C. or above for an Fe-Cr-Al-base alloy) is as follows.Specifically, when the foil material is as rolled or as annealed at atemperature below the recrystallization temperature, since the workedmicro structure derived from the rolling remains as it is, there is apossibility that the material temporarily exhibits a high proof stress.Even though the proof stress is improved in this state, the proof stressderived from the worked micro structure disappears accompanying thedisappearance of the worked micro structure in a high temperature regionwhere the maximum temperature reaches 950° C., so that there is apossibility that a desired proof stress cannot be maintained. For thisreason, the proof stress should be specified with the material asannealed at a temperature of the recrystallization temperature or aboveat which the worked micro structure disappears.

In the present invention, the strain rate used in specifying the proofstress is one used in the conventional method, that is, the tensile testspecified in JIS, that is, 0.1%/min.

This is because the order of the strain rate coincides with that of thehoneycomb material as the metallic carrier in a thermal shock test, thatis, the strain rate is not very different from that of the honeycombmaterial as the metallic carrier in a thermal shock test, so that theuse of the above-described strain rate is suitable for the evaluation ofphenomena caused in the actual honeycomb materials.

As described above, in the present invention, given amounts of Nb, Ta,Mo and W are added as means for enhancing the proof stress of thehoneycomb foil material at 600° C. and 700° C. The effect attained byadding these elements will now be described in terms of the addition ofNb.

FIG. 3 is a diagram provided by plotting data obtained by subjecting amaterial comprising 20% of Cr, 5% of Al and 0.01% of C and, addedthereto, 0 to 2.0% of Nb to the measurement of proof stresses at 600°C., 700° C. and 800° C. In the material containing Nb, both the proofstresses at 600° C. and 700° C. are improved over those of the materialnot containing Nb. In particular, when the amount of Nb added is 1%, theproof stress at 600° C. of the material is twice (about 30 kgf/mm²) theproof stress (about 15 kgf/mm²) of the material not containing Nb andthe proof stress at 700° C. of the material is about 3.5 times (about 24kgf/mm²) the proof stress (7 kgf/mm²) of the material not containing Nb,that is, an enhancement in the proof stress is significant. It is notedthat, at 800° C., the proof stress of the material containing Nb issubstantially the same as that of the material not containing Nb and noeffect can be attained by the addition of Nb. From these results, it isapparent that a marked improvement in the proof stresses at 600° C. and700° C. can be attained by the addition of Nb.

FIG. 4 is a diagram provided by plotting data obtained by subjecting amaterial comprising the same base alloy as shown in FIG. 3 and, addedthereto, 0.3% of Nb in combination with 0 to 4.0% of Mo to themeasurement of proof stresses in the temperature range of 600° to 800°C. The effect of Nb and Mo added in combination is apparent from FIG. 4.

In the honeycomb material of the present invention, besides thehigh-temperature proof stress improving elements, Ln (Ln being at leastone element selected from the group consisting of La, Pr, Ce and Nd) orY is added for the purpose of improving the oxidation resistance and theadhesion of an oxide film. A problem of a lowering in the hotworkability due to the addition of Ln as disclosed in Japanese ExaminedPatent Publication (Kokoku) No. 2-58340 and Japanese Unexamined PatentPublication (Kokai) No. 63-45351 can be solved by the combined use of Pand Ln. When Y is added, a more inexpensive Y misch (hereinafterreferred to as "Ym") may be used for the purpose of minimizing the costfor ingredients of the foil. Ym comprises about 60% of Y, about 35% ofheavy rare earth elements (Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) and about5% of light rare earth elements (La, Ce, Pr, Nd, Pm, Sm and Eu).

As described above, the honeycomb material of the present invention canprovide a metallic carrier that is excellent in not onlyhigh-temperature proof stress but also oxidation resistance, adhesion ofthe oxide film and hot workability and can sufficiently withstand heateven when exposed to an exhaust gas having a temperature of 900° C. orabove.

Chemical ingredients capable of realizing the high-temperature proofstress contemplated in the present invention will now be described.

The heat resistant stainless steel foil material of the presentinvention may be a steel product comprising, in terms of % by weight,more than 0.01 to 0.5% of Y, 4.5 to 6.5% of Al, 13 to 25% of Cr, 0.025%or less of C and 0.02% or less of N, the total of C and N being 0.03% orless, and, further, at least one member selected from the groupconsisting of (93.C/12+93.N/14)×1.1% to 3% of Nb,(181.C/12+181.N/14)×1.5% to 3% of Ta, 1 to 4% of Mo and 1 to 4% of W,the total of Nb and Ta being 3% or less, the total of Mo and W being 4%or less, with the balance consisting of Fe and unavoidable impurities.

Further, the above-described heat resisting stainless steel foilmaterial may be a steel product comprising, in terms of % by weight,more than 0.01 to 0.5% of Ym, 4.5 to 6.5% of Al, 13 to 25% of Cr, 0.025%or less of C and 0.02% or less of N, the total of C and N being 0.03% orless, and, further, at least one member selected from the groupconsisting of (93.C/12+93.N/14) ×1.1% to 3% of Nb,(181.C/12+181.N/14)×1.5% to 3% of Ta, 1 to 4% of Mo and 1 to 4% of W,the total of Nb and Ta being 3% or less, the total of Mo and W being 4%or less, with the balance consisting of Fe and unavoidable impurities.

Further, the above-described heat resisting stainless steel foilmaterial may be a steel product comprising, in terms of % by weight,more than 0.01 to 0.5% of Y, 4.5 to 6.5% of Al, 13 to 25% of Cr, 0.02%to (0.03+4.C+24.N/7) % of Ti, more than (93.C/12+93.N/14) % to 2.0% ofNb, 0.025% or less of C and 0.02% or less of N, the total of C and Nbeing 0.03% or less, with the balance consisting of Fe and unavoidableimpurities.

Further, the above-described heat resisting stainless steel foilmaterial may be a steel product comprising, in terms of % by weight,more than 0.01 to 0.5% of Ym, 4.5 to 6.5% of Al, 13 to 25% of Cr, 0.02%to (0.03+4.C+24.N/7) % of Ti, more than (93.C/12+93.N/14) % to 2.0% ofNb, 0.025% or less of C and 0.02% or less of N, the total of C and Nbeing 0.03% or less, with the balance consisting of Fe and unavoidableimpurities.

Further, the above-described heat resisting stainless steel foilmaterial may be a steel product comprising, in terms of % by weight,more than 0.06 to 0.15% of Ln, 8×(Ln+0.015)/45% to 0.1% of P, 4.5 to6.5% of Al, 13 to 25% of Cr, 0.025% or less of C and 0.02% or less of N,the total of C and N being 0.03% or less, and, further, at least onemember selected from the group consisting of (181.C/12+181.N/14)×1.5% to3% of Ta, (93.C/12+93.N/14)×1.1% to 3% of Nb, 1 to 4% of Mo and 1 to 4%of W, the total of Ta and Nb being 3% or less, the total of Mo and Wbeing 4% or less, with the balance consisting of Fe and unavoidableimpurities.

Further, the above-described heat resisting stainless steel foilmaterial may be a steel product comprising, in terms of % by weight,more than 0.06 to 0.15% of Ln, 8×(Ln+0.015)/45% to 0.1% of P, 4.5 to6.5% of Al, 13 to 25% of Cr, 0.02% to (0.03+4.C+24.N/7) % of Ti, morethan (93.C/12+93.N/14) % to 2.0% of Nb, 0.025% or less of C and 0.02% orless of N, the total of C and N being 0.03% or less, with the balanceconsisting of Fe and unavoidable impurities.

The reason for the limitation of the above-described ingredients willnow be described.

(1) Ta:

Ta is an additive element important to the present invention from theviewpoint of improving the proof stress of the foil at high temperaturesand improving the durability of the structure of the carrier for acatalyst. Ta combines with C and N contained in the steel to form acarbonitride that gives rise to the so-called "precipitationstrengthening". In addition, excess carbonitride is dissolved in a solidsolution form in the matrix to cause solid solution strengthening, andthese contributes to an improvement in the high-temperature proofstress. In this case, the effect of precipitation strengthening islarge. However, precipitates often aggregate and coarsen during use ofthe carrier, for example, at a temperature exceeding 750° C. for a longperiod of time to cause a change in the metallic structure, which lowersthe effect of precipitation strengthening. On the other hand, althoughthe effect of solid solution strengthening is not as large as the effectof precipitation strengthening, no significant lowering in theabove-described function and effect attributable to a change in themetallic structure occurs even when the carrier was used for a longperiod of time. For this reason, even when the precipitationstrengthening is lost by the above-described-phenomenon, it is necessaryto add Ta in a somewhat excess over the amount of C and N for thepurpose of sustaining the solid solution strengthening effect. Studiesconducted by the present inventors from this point of view have revealedthat the addition of Ta in an amount of (181.C/12+181.N/14)×1.5% or moreis necessary.

However, the presence of an extreme excess of Ta causes a Laves phase tobe precipitated, a steel ingot as cast to become liable to crack and,further, the high-temperature proof stress to fall. The Ta content is 3%from the viewpoint of the relationship thereof with the C content and Ncontents specified in the present invention. For the reasons set outabove, the amount range of Ta added is as follows.

    Ta: (181.C/12+181.N/14)×1.5% to 3%

Further, since Ta immobilizes C and N, it has the effect of improvingthe toughness of the hot-rolled sheet. This effect can be sufficientlyattained when Ta is added in the above-described amount range.

(2) Nb:

As with Ta, Nb is an additive element important to the present inventionfrom the viewpoint of improving the proof stress of the foil at hightemperatures and improving the durability of the structure of thecarrier for a catalyst. As with Ta, Nb serves to improve thehigh-temperature proof stress by taking advantage of both precipitationstrengthening and solid solution strengthening. Further, as with Ta, theamount range of Nb added is limited by the relationship thereof with theamounts of C and N, and the amount of Nb should be at least(93.C/12+93.N/14)×1.1%.

On the other hand, as with Ta, Nb forms a Laves phase when it is addedin an extreme excess, which leads to the same adverse effect asdescribed above in connection with Ta. The upper limit of the Nb contentis specified from this point of view. According to studies conducted bythe present inventors, it is 3%. For the reasons set out above, theamount range of Nb added is as follows.

    Nb: (93.C/12+93.N/14)×1.1% to 3%

Further, Nb has the effect of significantly improving the toughness ofthe hot-rolled sheet. This effect can be sufficiently attained when Tais added in the above-described amount range.

For the same reason, when Ta and Nb are added in combination, the upperlimit of the total amount Ta and Nb is 3%.

When Nb is added in combination with Ti, which will be described later,the amount of Nb added is separately specified.

When the high-temperature proof stress is improved by taking advantageof the solid solution strengthening by the addition of a relativelylarge amount of Mo and/or W, the addition of an excessive amount of Nbcauses the steel ingot as cast to become liable to crack during coolingand, at the same time, sometimes deteriorates the hot workability andtoughness. For this reason, the upper limit of the amount of Nb added ispreferably (93.C/12+93.N/14)×4.5% which causes the effect of improvingthe toughness to begin to become saturated.

(3) Mo and W:

Mo or W is an additive element important to the present inventionparticularly from the viewpoint of improving the high-temperature proofstress and the durability of the structure of the carrier for acatalyst. Mo and W are dissolved in a solid solution form in the matrixof the steel to improve the high-temperature proof stress by takingadvantage of solid solution strengthening. In this case, considerableamounts of Mo and W can be dissolved in a solid solution form withoutthe formation of a detrimental precipitate phase, which contributes to amarked improvement in strengthening. Further, since they cause nosignificant change in the metallic structure, the strengthening effecthardly changes with time.

The amount of Mo and/or W added is determined from this point of view.According to the results of studies conducted by the present inventors,the amount of Mo added should be 1% or more for the purpose of attaininga satisfactory solid solution strengthening effect, and the lower limitof the amount of W added is also 1%.

Since a large part of both Mo and W are dissolved in a solid solutionform, the metallic matrix is strengthened with an increase in the amountof Mo and W added. However, the addition of excessive amounts of Mo andW results in a lowering in toughness. Therefore, the amounts of Mo and Wadded are limited from this point of view, and the upper limit is 4% forboth the elements. The same effect can be attained when Mo and W areadded in combination. In this case, the upper limit of the total amountof Mo and W is preferably 4%.

As described above, in the present invention, the high-temperature proofstress can be improved by the addition of a suitable amount of Ta and/orNb. In the strengthening effect exerted by Ta and Nb, in some cases, theprecipitation strengthening effect is gradually deteriorated during useof the carrier at a high temperature, and the addition of these elementsin an excessive amount unfavorably lowers the high-temperature proofstress. By contrast, the effect attained by the addition of Mo and/or Wis not influenced by the presence of Ta and/or Nb, and Mo and W can bedissolved in considerable amounts in the matrix without the formation ofany detrimental precipitate phase to provide a significant solidsolution effect. That is, the addition of Mo and/or W to an alloy havinga high-temperature strength improved by the addition of Ta and/or Nbenables the high-temperature proof stress to be further improved.

(4) Ti:

Ti is an additive element important to the present invention because itcan improve the high-temperature proof stress when added in combinationwith Nb.

As described above, in order to improve the durability of the structureof the carrier for a catalyst, it is important to improve thehigh-temperature proof stress of the foil and, at the same time, toprevent the lowering in the improved proof stress even after heating fora long period of time. In the strengthening effect exerted by theaddition of Ta or Nb, since the precipitation strengthening effect isattained mainly by the precipitation of a carbonitride formed bycombining of Ta or Nb with C and N, in some cases, the carbonitride isgradually deteriorated during use of the carrier at a high temperature,which deteriorates the strengthening effect.

However, it is considered that, when a considerable amount of Nb isadded after the addition of a minor amount of Ti, since C and N areprecipitated as a Ti-based carbonitride, Nb can be dissolved in a solidsolution form without forming a significant amount of a Nb-basedcarbonitride. This enables a relatively large strengthening effect to bestably attained particularly at high temperatures. Further, since Ticauses no significant change in the metallic structure even when heatingis effected at a high temperature for a long period of time, thestrengthening effect hardly changes with time. Further, as describedabove, since Ti immobilizes C and N in a solid solution form, it canimprove the toughness of the hot-rolled sheet.

The amount of Ti and Nb added in combination is determined from thispoint of view. According to the results of studies conducted by thepresent inventors, in order to attain a satisfactory solid solutionstrengthening effect, Ti should be added in an amount of 0.2% incombination with Nb in an amount exceeding (93.C/12+93.N/14) %. However,when the amount of Ti added is excessive, Ti forms a number of coarsesquare Ti-based precipitates having a size exceeding 10 μm and Nb formNb forms a Nb-based intermetallic compound, which gives rise to adeterioration in the hot workability and the toughness of the hot-rolledsheet. The amounts of Ti and Nb added are limited from this point ofview, and the upper limits of Ti and Nb contents are (0.03+4.C+24.N/7) %and 2.0%, respectively. It is noted that the addition of Ti and Nb inthe above-described respective amount ranges has no adverse effect onthe oxidation resistance of the foil. Ti is preferably added before theaddition of Nb during the production of the steel by the melt process.

(5) C and N:

In the present invention, C and N cause a marked lowering in thetoughness of the hot-rolled sheet. Although this adverse effect can beprevented by the action of Ta or Nb, the restoration of toughnessbecomes difficult when the C content exceeds 0.025%, the N contentexceeds 0.02% or the total content of C and N exceeds 0.03%.

For this reason, the C content should be 0.025% or less, and the Ncontent should be 0.02% or less, provided that the total content of Cand N is 0.03% or less.

C and N precipitate as a carbonitride that exhibits such a favorablefunction and effect that the high-temperature proof stress is improvedby the precipitation strengthening effect. As described above, thecoarsening of the precipitates deteriorates this effect. When C and Nare contained in large amounts in the steel, even though Ta and/or Nbare added in amounts exceeding the above-described lower limit values,the coarsening of the precipitates are accelerated to increases the rateof deterioration of the strengthening effect. That is, when C and N arecontained in large amounts, the average grain size of the carbonitridebecomes so large that it becomes difficult to attain homogeneous fineprecipitation useful for precipitation strengthening. The contents of Cand N are limited from this point of view, and in the present invention,the C content is 0.025% or less, the N content is 0.02% or less and thetotal content of C and N is 0.03% or less.

For the reasons set out above, the C and N contents should satisfy thefollowing requirements.

C: 0.025% or less,

N: 0.02% or less, and

C+N: 0.03% or less.

(6) Y and Ym:

Y has the effect of improving the oxidation resistance and theresistance to abnormal oxidation of the foil. When the Y content exceeds0.01%, a marked improvement in the time to the occurrence of abnormaloxidation, i.e., service life of the foil, can be attained over theservice life of the foil having an Y content of 0.01% or less. However,when the Y content exceeds 0.5%, the service life again begins to lower.For this reason, the Y content is limited to more than 0.01 to 0.05%.

In the present invention, the so-called "Ym" which is more inexpensive,may be used as the actual additive material. As with the addition of Y,when the Ym content exceeds 0.01%, the service life of the foil, whichis the time to the occurrence of the abnormal oxidation, can besignificantly improved in comparison to the foil having a Ym content of0.01 or less. However, when the Ym content exceeds 0.5%, the servicelife again begins to lower. For this reason, the Ym content is limitedto more than 0.01 to 0.05%.

Even when Y is added in a large amount, the hot workability of the steelremains good as opposed to the Ln (lanthanoide) described below thatlowers the hot workability when it is added in a large amount. This isbecause the addition of a large amount of Ln causes a low-meltingCe-rich phase, whereas the addition of a large of Y causes the Y to forma high-melting-point intermetallic compound with Fe. For this reason,when use is made of a large-size steel ingot having a large segregationratio which has been mass-produced in a works, the addition of Y or Ymis more advantageous than the addition of Ln.

(7) Ln (lanthanoide):

Ln (lanthanoide) is a generic name for 15 elements beginning with La andending with Lu in the period table. In the present invention, theso-called "misch metal", which is more inexpensive, may be actuallyadded as a raw material for Ln. In this case, when the misch metal isanalyzed, four elements of La, Ce, Pr and Nd are detected with otherelements, i.e., Pm, Sm, Eu and Gd, that are present in very smallamounts and hence negligible. Therefore, Ln used in the presentinvention can be regarded as a mixture of the above-described fourelements.

When at least one element selected from La, Ce, Pr and Nd is addedinstead of the misch metal, the effect attained is equivalent to thatattained by the misch metal. Therefore, the Ln of the present inventionincludes also these elements.

Ln has the effect of improving the resistance to abnormal oxidation ofthe foil in an exhaust gas. When the Ln content exceeds 0.06%, theservice life of the foil, which is the time to the occurrence ofabnormal oxidation in an exhaust gas, can be significantly improved incomparison to the foil having a Ln content of 0.06% or less. However,when the Ln content exceeds 0.15%, the service life again begins tolower. For this reason, the Ln content is limited to more than 0.06 to0.15%.

(8) P:

P is an element important to the present invention from the viewpoint ofimproving the hot workability in relation to Ln.

Specifically, in the present invention, the addition of Ln in an amountin the above-described range enables the oxidation resistance of thefoil to be significantly improved. In the prior art, however, therecognition with respect to the addition of Ln was that the addition ofLn is detrimental to the hot workability, which makes it difficult toproduce a foil in the conventional process for mass-producing astainless steel sheet through a hot-rolled coil. This difficulty hasbeen considered attributable to the fact that Ce as a main ingredient ofthe misch metal is liable to form a low-melting-point Ce-rich phase.However, it is noted that, when Ln is added in a large amount, theaddition of Ln in combination with P causes, for example, part of Ce andLa to exist as a relatively fine particulate high-melting-pointphosphide having a size of 3 μm or less in the steel, so that thelowering in the hot workability does not occur at all. With respect tothe P content necessary for this purpose, studies conducted by thepresent inventors have revealed that the lower limit of the P content is8×(Ln+0.015)/45% on the premise that the Ln content is in the range offrom more than 0.06 to 0.15% and use is made of a large-size steel ingothaving a high segregation ratio which has been mass-produced in a steelmill. When Ln is not added, there is no need of specifying the lowerlimit of the P content.

On the other hand, since P lowers the toughness of a ferritic stainlesssteel, the P content is limited from this point of view for theFe-Cr-Al-base stainless steel inherently having a poor toughness, sothat, in the present invention, the upper limit of the P content is0.1%. The addition of P in an amount in the above-described range has noadverse effect on the oxidation resistance of the foil.

(9) Al:

Al is an fundamental element indispensable to the present invention forensuring the oxidation resistance. In the case of a foil, when the Alcontent of the foil is less than 4.5%, the protection of the oxide filmin an exhaust gas is so poor that abnormal oxidation is liable to occur,which renders the foil unsatisfactory for use as the catalyst carrier.On the other hand, when the Al content exceeds 6.5%, the toughness ofthe hot-rolled sheet is extremely lowered, which is detrimental to theproducibility. In addition, the coefficient of thermal expansion of thefoil becomes so large that, if such a foil is used as a catalystcarrier, the thermal fatigue accompanying the repetition of heating andcooling is large. For this reason, in the present invention, the Alcontent is in the range of from 4.5 to 6.5%.

(10) Cr:

Cr is a fundamental element indispensable to the present invention forensuring the corrosion resistance of the stainless steel. In the presentinvention, although the oxidation resistance derives mainly from an Al₂O₃ film, lack of Cr gives rise to a deterioration in the adhesion andprotection of the Al₂ O₃. On the other hand, when the Cr content isexcessively high, the toughness of the hot-rolled sheet is deteriorated.For this reason, the Cr content is limited to 13 to 25%.

(11) Si:

Si has an adverse effect on the present invention and deteriorates thetoughness of the hot-rolled sheet. Therefore, it is preferred to limitthe Si content to about 0.5% or less that being the amount of Siinevitably included in common stainless steels.

(12) Other impurities:

Mn: Mn is concentrated within the oxide film particularly in a veryearly stage of the formation of the oxide film and is detrimental to theformation of the Al₂ O₃ film after that, which is causative of thestructural defect of the film, so that in the present invention it ispreferred to limit the Mn content to 0.3% or less.

S: S deteriorates the oxidation resistance, so that in the presentinvention it is preferred to limit the S content to 0.003% or less.

Ni: Ni is strongly combined with Al to render the Fe-Cr-Al-base alloyremarkably brittle, so that in the present invention the Ni content islimited to 0.3% or less.

An about 50 μm-thick foil can be produced from the Fe-Cr-Al-base alloyhaving the above-described constitution according to the presentinvention by combining steps used for the mass production ofconventional ferritic stainless steels, that is, steps of melting, hotrolling and cold rolling, optionally with the step of annealing.Further, the foil thus produced and a carrier for an exhaust gaspurification catalyst and an exhaust gas purification catalyst deviceconstructed using this foil exhibit a very high degree of resistance tothe occurrence of abnormal oxidation even in a combustion exhaust gasatmosphere having a high temperature region of 900° C. or above and, inaddition, a high degree of resistance to thermal fatigue as a honeycombby virtue of a high proof stress at high temperatures of the foil, sothat the structural durability is excellent even under serviceconditions where heating and cooling cycle are repeated.

EXAMPLES

The effect of the present invention will now be described in moredetail.

Example 1

The chemical ingredients of the heat-resistant stainless steelsaccording to the present invention and comparative materials are givenin Table 1. All the materials are based on 20Cr-5Al, and the steelsaccording to the examples of the present invention (A1 to A18) comprisethe 20Cr-5Al and, added thereto, Y for the purpose of ensuring theoxidation resistance and Nb, Ta, Mo and W, either alone or incombination, for the purpose of enhancing the high-temperature proofstress. The comparative materials (A19 to A24) comprise the 20Cr-5Alalone with no strengthening element added or the 20Cr-5Al with, addedthereto, Ti or the like.

100 kg of each of the steels specified in Table 1 was melted in a vacuumhigh frequency furnace, cast, heated to 1,200° C., hot-rolled with areduction ratio of 30%, air-cooled, held at 1,150° C. for one hr andhot-rolled immediately after the completion of the holding into 4mm-thick steel sheets that were then air cooled. The hot-rolled sheetswere descaled by shot blasting, pickling, etc. and subjected to a seriesof steps of cold rolling (some alloys being hot-rolled), annealing anddescaling to provide foil coils having a sheet thickness of about 50 μm.In this case, all the steels according to the examples of the presentinvention exhibited a good hot workability and a good toughness in theform of hot-rolled sheets.

When the foil materials were in a thin sheet form, they were annealed at1,200° C. for 15 min and specimens for a high-temperature tensile testwere sampled and subjected to a high-temperature tensile test accordingto the method specified in JIS to measure proof stresses at 600° C. and700° C. Since the high-temperature proof stress of the thin sheet isfundamentally equivalent to that of the foil material, in the presentinvention, the high-temperature proof stress of the material in the formof a thin sheet was adopted because of the higher accuracy ofmeasurement. The results are given in the column of the high-temperatureproof stress of Table 2. Whether or not an increase in thehigh-temperature proof stress contemplated in the present inventioncould be attained was judged by comparing the measured values withstandards, i.e., a proof stress of 22 kgf/mm² or more at 600° C. and aproof stress of 11 kgf/mm² or more at 700° C., and the proof stress wasevaluated as O when the measured value met the standard while the proofstress was evaluated as X when the measured value did not meet thestandard. The proof stress values are each the average of threeexperimental values. All the alloys according to the examples of thepresent invention exhibited a good high-temperature proof stress.

The oxidation resistance of each foil material was evaluated as follows.A specimen having a sheet thickness of 50 μm, a width of 20 mm and alength of 25 mm was sampled from a foil coil and subjected to anoxidation test in a heating furnace into which an exhaust gas wasdischarged from a gasoline engine. In this case, a test wherein thespecimen was heated to 1,150° C. for 25 hr and then allowed to cool wascarried out until abnormal oxidation occurred. The results are given inthe column of the oxidation resistance of Table 2. The foil materialhaving an abnormal oxidation life of 200 hr or more was evaluated as Owhile the foil material having an abnormal oxidation life of less than200 hr was evaluated as X. All the steel foils according to the examplesof the present invention exhibited a long life of 200 hr or more.

Then, a metallic carrier shown in FIG. 5, that is, a metallic carrierhaving a capacity of 1 liter (113 mmφ×1000 mm in length), was preparedusing a corrugated sheet 3 formed by corrugating the above-describedfoil, the above-described foil strip (a flat sheet) 2 subjected to noworking and a cylindrical jacket 1 of a ferritic stainless steel havinga sheet thickness of 1.5 mm. A catalyst was supported on the carrier andapplied to an engine bench test.

The engine bench test of the metallic support was carried out bymounting the catalyst supported on the metallic carrier on an exhaustgas path of an engine and effecting a thermal shock test wherein aheating-cooling cycle with the maximum temperature and the minimumtemperature of the inlet exhaust gas being 950° C. and 150° C.,respectively, was repeated 1200 times. When unfavorable displacement ofthe metallic carrier occurred during the test, the test was stopped atthat time. The term "unfavorable displacement" used herein is intendedto mean such an unfavorable phenomenon that breaking of the foil occursover the whole periphery of the honeycomb to cause the honeycomb to bemoved back in the direction of flow of the exhaust gas. The results aregiven in Table 2. When the metallic support passed the thermal shocktest, it was evaluated as O, while when the metallic support did notpass the thermal shock test, it was evaluated as X. After the test,although the honeycombs according to the examples of the presentinvention also had slight cell deformation, they had no severe damage,whereas the comparative supports suffered from not only unfavorabledisplacement in the direction of flow of the exhaust gas but also severedamage, such as collapse of cell and foil breaking. In all thehoneycombs of the examples of the present invention, the blistering (anincrease in the length of the honeycomb) was 3% or less.

As is apparent from Table 2, the metallic carriers using the comparativefoil materials having low proof stresses at 600° C. and 700° C. couldnot withstand a 1,200-cycle high-temperature thermal shock durabilitytest, whereas all the metallic carriers using the foil materials havinghigh proof stresses at 600° C. and 700° C. gave rise to no unfavorabledisplacement even after the 1,200-cycle thermal shock durability testand passed the high-temperature thermal shock durability test. That is,the metallic carriers using the foil materials having enhanced proofstresses at 600° C. and 700° C. were excellent in the structuraldurability of the honeycomb. Further, in the metallic carriers accordingto the examples of the present invention, the occurrence of abnormaloxidation was not observed even after the durability test, and the Alconsumption of the foil was as low as about 2%, which demonstrates thatthese carriers have also a good oxidation resistance.

                                      TABLE 1                                     __________________________________________________________________________    (wt. %)                                                                       Mark    C  N   C + N                                                                             Cr Al Nb  Ta  Nb + Ta                                                                            Mo   W  Mo + W                                                                              Y  Others                 __________________________________________________________________________    Ex. A1  0.008                                                                            0.0060                                                                            0.0140                                                                            20.36                                                                            5.11                                                                             0.30                                                                              --  0.30 --   -- --    0.081                                                                            --                     Ex. A2  0.007                                                                            0.0048                                                                            0.0118                                                                            20.13                                                                            5.31                                                                             --  1.18                                                                              1.18 --   -- --    0.073                                                                            --                     Ex. A3  0.007                                                                            0.0060                                                                            0.0130                                                                            19.96                                                                            5.14                                                                             --  --  --   2.71 -- 2.71  0.101                                                                            --                     Ex. A4  0.008                                                                            0.0065                                                                            0.0145                                                                            21.19                                                                            5.29                                                                             --  --  --   --   2.63                                                                             2.63  0.086                                                                            --                     Ex. A5  0.009                                                                            0.0068                                                                            0.0158                                                                            20.64                                                                            5.23                                                                             0.31                                                                              0.62                                                                              0.93 --   -- --    0.070                                                                            --                     Ex. A6  0.008                                                                            0.0074                                                                            0.0154                                                                            20.31                                                                            5.26                                                                             0.30                                                                              --  0.30 1.51 -- 1.51  0.079                                                                            --                     Ex. A7  0.009                                                                            0.0057                                                                            0.0147                                                                            20.94                                                                            5.11                                                                             0.31                                                                              --  0.31 --   1.03                                                                             1.03  0.083                                                                            --                     Ex. A8  0.007                                                                            0.0037                                                                            0.0107                                                                            19.84                                                                            4.99                                                                             --  0.83                                                                              0.83 1.02 -- 1.02  0.097                                                                            --                     Ex. A9  0.012                                                                            0.0041                                                                            0.0161                                                                            19.64                                                                            5.00                                                                             --  0.92                                                                              0.92 --   1.49                                                                             1.49  0.075                                                                            --                     Ex. A10 0.007                                                                            0.0038                                                                            0.0108                                                                            20.30                                                                            5.10                                                                             --  --  --   1.50 1.23                                                                             2.73  0.074                                                                            --                     Ex. A11 0.006                                                                            0.0040                                                                            0.0100                                                                            20.10                                                                            4.99                                                                             0.30                                                                              --  0.30 1.09 1.40                                                                             2.49  0.097                                                                            --                     Ex. A12 0.008                                                                            0.0039                                                                            0.0119                                                                            20.64                                                                            5.21                                                                             0.30                                                                              0.52                                                                              0.82 --   1.08                                                                             1.08  0.089                                                                            --                     Ex. A13 0.008                                                                            0.0043                                                                            0.0123                                                                            19.97                                                                            5.36                                                                             0.32                                                                              0.63                                                                              0.95 1.21 -- 1.21  0.069                                                                            --                     Ex. A14 0.008                                                                            0.0049                                                                            0.0129                                                                            20.32                                                                            5.16                                                                             --  0.81                                                                              0.81 1.10 1.05                                                                             2.15  0.085                                                                            --                     Ex. A15 0.012                                                                            0.0045                                                                            0.0165                                                                            20.64                                                                            5.21                                                                             0.30                                                                              0.53                                                                              0.83 1.30 1.15                                                                             2.45  0.078                                                                            --                     Ex. A16 0.012                                                                            0.0042                                                                            0.0162                                                                            19.74                                                                            5.28                                                                             0.32                                                                              --  0.32 --   -- --    0.056                                                                            --                     Ex. A17 0.006                                                                            0.0039                                                                            0.0099                                                                            20.54                                                                            5.36                                                                             0.31                                                                              --  0.31 1.52 -- 1.52  0.049                                                                            --                     Ex. A18 0.010                                                                            0.0036                                                                            0.0136                                                                            20.20                                                                            5.34                                                                             0.32                                                                              --  0.32 1.19 -- 1.19  0.051                                                                            --                     Comp.                                                                             A19 0.007                                                                            0.0049                                                                            0.0119                                                                            20.10                                                                            5.28                                                                              --*                                                                               --*                                                                               --*  --*  --*                                                                              --*  --*                                                                              Ln = 0.08*             Ex.                                                                           Comp.                                                                             A20 0.008                                                                            0.0060                                                                            0.0140                                                                            20.34                                                                            5.24                                                                              --*                                                                               --*                                                                               --*  --*  --*                                                                              --*  --*                                                                              Ln = 0.107*            Ex.                                                    Ti = 0.05              Comp.                                                                             A21 0.015                                                                            0.0083                                                                            0.0233                                                                            20.31                                                                            5.29                                                                              0.11*                                                                            --   0.11*                                                                             --   -- --    0.082                                                                            --                     Ex.                                                                           Comp.                                                                             A22 0.008                                                                            0.0054                                                                            0.0134                                                                            19.99                                                                            5.34                                                                             --  --  --    0.81*                                                                             --  0.81*                                                                              0.069                                                                            --                     Ex.                                                                           Comp.                                                                             A23 0.006                                                                            0.0090                                                                            0.0150                                                                            20.01                                                                            5.10                                                                              --*                                                                               --*                                                                               --*  --*  --*                                                                              --*  --*                                                                              La = 0.07*             Ex.                                                                           Comp.                                                                             A24 0.014                                                                            0.0052                                                                            0.0192                                                                            20.7                                                                             5.20                                                                             --   0.37*                                                                             0.37*                                                                             --   -- --    0.086                                                                            --                     Ex.                                                                           __________________________________________________________________________     Note) *: Outside the scope of the invention                              

                                      TABLE 2                                     __________________________________________________________________________    Classification            High-temp.                                          of foil                                                                              Main ingredients other than                                                                      proof stress                                                                          Oxidation                                                                           Results of engine bench                                                       durability test                       materials                                                                            Cr and Al in foil material                                                                       600° C.                                                                    700° C.                                                                    resistance                                                                          Unfavorable displacement                                                                         Results            __________________________________________________________________________    A1 Ex. 0.3Nb--0.08Y       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A2 Ex. 1.2Ta--0.07Y       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A3 Ex. 2.7Mo--0.1Y        ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A4 Ex. 2.6W--0.09Y        ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A5 Ex. 0.3Nb--0.6Ta--0.07Y                                                                              ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A6 Ex. 0.3Nb--1.5Mo--0.08Y                                                                              ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A7 Ex. 0.3Nb--1W--0.08Y   ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A8 Ex. 0.8Ta--1Mo--0.1Y   ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A9 Ex. 0.9Ta--1.5W--0.08Y ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A10                                                                              Ex. 1.5Mo--1.2W--0.07Y ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A11                                                                              Ex. 0.3Nb--1Mo--1.4W--0.1Y                                                                           ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A12                                                                              Ex. 0.3Nb--0.5Ta--1W--0.09Y                                                                          ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A13                                                                              Ex. 0.3Nb--0.6Ta--1.2Mo--0.07Y                                                                       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A14                                                                              Ex. 0.8Ta--1.1Mo--1W--0.09Y                                                                          ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A15                                                                              Ex. 0.3Nb--0.5Ta--1.3Mo--1.1W--0.08Y                                                                 ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A16                                                                              Ex. 0.3Nb--0.06Y       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A17                                                                              Ex. 0.3Nb--1.5Mo--0.05Y                                                                              ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A18                                                                              Ex. 0.3Nb--1Mo--0.05Y  ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      A19                                                                              Comp.                                                                             0.08Ln             X   X   ◯                                                                       Displaced after 550                                                                              Xycles                Ex.                                                                        A20                                                                              Comp.                                                                             0.107Ln--0.05Ti    X   X   ◯                                                                       Displaced after 740                                                                              Xycles                Ex.                                                                        A21                                                                              Comp.                                                                             0.1Nb--0.08Y       ◯                                                                     X   ◯                                                                       Displaced after 850                                                                              Xycles                Ex.                                                                        A22                                                                              Comp.                                                                             0.8Mo--0.07Y       X   X   ◯                                                                       Displaced after 860                                                                              Xycles                Ex.                                                                        A23                                                                              Comp.                                                                             0.07La             X   X   ◯                                                                       Displaced after 600                                                                              Xycles                Ex.                                                                        A24                                                                              Comp.                                                                             0.4Ta--0.09Y       ◯                                                                     X   ◯                                                                       Displaced after 650                                                                              Xycles                Ex.                                                                        __________________________________________________________________________

Example 2

The chemical ingredients of the heat-resistant stainless steelsaccording to the present invention and comparative materials are givenin Table 3. All the materials are based on 20Cr-5Al, and the steelsaccording to the examples of the present invention (B1 to B18) comprisethe 20Cr-5Al and, added thereto, Ym for the purpose of ensuring theoxidation resistance and Nb, Ta, Mo and W, either alone or incombination, for the purpose of enhancing the high-temperature proofstress. The comparative materials (B19 to B22) comprise 20Cr-5Al alonewith no strengthening element added or 20Cr-5Al with, added thereto, Tior the like.

The procedure of Example 1 was repeated to prepare foil materials andmetallic carriers that were then subjected to the measurement of thehigh-temperature proof stress, evaluation of the oxidation resistanceand engine bench test in the same manner as that of Example 1. In thiscase, all the steels according to the examples of the present inventionhad a good hot workability and a good toughness in the form of ahot-rolled sheet. The results are summarized in Table 4. As is apparentfrom Table 4, the metallic carriers using the comparative foil materialshaving low proof stresses at 600° C. and 700° C. could not withstand the1200-cycle high-temperature thermal shock durability test, whereas allthe metallic carriers using the foil materials having high proofstresses at 600° C. and 700° C. and a good oxidation resistance gaverise to no unfavorable displacement even after the 1,200-cycle thermalshock durability test and passed the high-temperature thermal shockdurability test. That is, the metallic carriers using the foil materialshaving enhanced proof stresses at 600° C. and 700° C. were excellent inthe structural durability of the honeycomb. Further, in the metalliccarriers according to the examples of the present invention, theoccurrence of abnormal oxidation was not observed even after thedurability test, and the Al consumption of the foil was as low as about2%, which demonstrates that these carriers have also a good oxidationresistance.

                                      TABLE 3                                     __________________________________________________________________________    (wt. %)                                                                       Mark    C  N   C + N                                                                             Cr Al Nb  Ta  Nb + Ta                                                                            Mo   W  Mo + W                                                                              Ym Others                 __________________________________________________________________________    Ex. B1  0.011                                                                            0.0085                                                                            0.0195                                                                            20.10                                                                            5.34                                                                             0.30                                                                              --  0.30 --   -- --    0.081                                                                            --                     Ex. B2  0.010                                                                            0.0088                                                                            0.0188                                                                            21.09                                                                            5.29                                                                             --  1.18                                                                              1.18 --   -- --    0.089                                                                            --                     Ex. B3  0.010                                                                            0.0071                                                                            0.0181                                                                            19.99                                                                            5.24                                                                             --  --  --   2.61 -- 2.61  0.101                                                                            --                     Ex. B4  0.007                                                                            0.0041                                                                            0.0111                                                                            20.09                                                                            5.28                                                                             --  --  --   --   2.50                                                                             2.50  0.086                                                                            --                     Ex. B5  0.006                                                                            0.0044                                                                            0.0104                                                                            20.30                                                                            5.19                                                                             0.31                                                                              0.90                                                                              1.21 --   -- --    0.091                                                                            --                     Ex. B6  0.008                                                                            0.0053                                                                            0.0133                                                                            20.10                                                                            5.23                                                                             0.30                                                                              --  0.30 1.61 -- 1.61  0.070                                                                            --                     Ex. B7  0.009                                                                            0.0063                                                                            0.0153                                                                            20.54                                                                            5.28                                                                             0.31                                                                              --  0.31 --   1.03                                                                             1.30  0.089                                                                            --                     Ex. B8  0.007                                                                            0.0066                                                                            0.0136                                                                            19.97                                                                            5.21                                                                             --  1.09                                                                              1.09 1.11 -- 1.11  0.097                                                                            --                     Ex. B9  0.008                                                                            0.0053                                                                            0.0133                                                                            19.99                                                                            5.16                                                                             --  0.99                                                                              0.99 --   1.44                                                                             1.44  0.078                                                                            --                     Ex. B10 0.009                                                                            0.0055                                                                            0.0145                                                                            20.31                                                                            5.16                                                                             --  --  --   1.61 1.11                                                                             2.72  0.076                                                                            --                     Ex. B11 0.011                                                                            0.0064                                                                            0.0174                                                                            20.34                                                                            5.21                                                                             0.31                                                                              --  0.31 1.02 1.11                                                                             2.13  0.081                                                                            --                     Ex. B12 0.008                                                                            0.0060                                                                            0.0140                                                                            20.10                                                                            4.99                                                                             0.30                                                                              0.81                                                                              1.11 --   1.02                                                                             1.02  0.069                                                                            --                     Ex. B13 0.007                                                                            0.0041                                                                            0.0111                                                                            20.20                                                                            5.10                                                                             0.31                                                                              0.72                                                                              1.03 1.19 -- 1.19  0.080                                                                            --                     Ex. B14 0.011                                                                            0.0085                                                                            0.0195                                                                            20.54                                                                            5.01                                                                             --  0.99                                                                              0.99 1.09 1.08                                                                             2.17  0.066                                                                            --                     Ex. B15 0.006                                                                            0.0057                                                                            0.0117                                                                            19.74                                                                            4.99                                                                             0.20                                                                              0.71                                                                              0.91 1.11 1.08                                                                             2.19  0.083                                                                            --                     Ex. B16 0.008                                                                            0.0075                                                                            0.0155                                                                            20.66                                                                            5.11                                                                             0.31                                                                              --  0.31 --   -- --    0.054                                                                            --                     Ex. B17 0.009                                                                            0.0067                                                                            0.0157                                                                            20.30                                                                            5.26                                                                             0.30                                                                              --  0.30 1.51 -- 1.51  0.049                                                                            --                     Ex. B18 0.008                                                                            0.0084                                                                            0.0164                                                                            21.15                                                                            5.23                                                                             0.29                                                                              --  0.29 1.12 -- 1.12  0.052                                                                            --                     Comp.                                                                             B19 0.007                                                                            0.0049                                                                            0.0119                                                                            20.10                                                                            5.28                                                                              --*                                                                               --*                                                                               --*  --*  --*                                                                              --*  -- Ln = 0.08*             Ex.                                                                           Comp.                                                                             B20 0.008                                                                            0.0060                                                                            0.0140                                                                            20.34                                                                            5.24                                                                              --*                                                                               --*                                                                               --*  --*  --*                                                                              --*  -- Ln = 0.107*            Ex.                                                    Ti = 0.05              Comp.                                                                             B21 0.012                                                                            0.0042                                                                            0.0162                                                                            19.97                                                                            5.21                                                                              --*                                                                               --*                                                                               --* 0.9* -- 0.9*  0.08                                                                             --                     Ex.                                                                           Comp.                                                                             B22 0.014                                                                            0.0052                                                                            0.0192                                                                            20.7                                                                             5.20                                                                             --   0.37*                                                                             0.37*                                                                             --   -- --    0.07                                                                             --                     Ex.                                                                           __________________________________________________________________________     Note) *: Outside the scope of the invention                              

                                      TABLE 4                                     __________________________________________________________________________    Classification            High-temp.                                          of foil                                                                              Main ingredients other than                                                                      proof stress                                                                          Oxidation                                                                           Results of engine bench                                                       durability test                       materials                                                                            Cr and Al in foil material                                                                       600° C.                                                                    700° C.                                                                    resistance                                                                          Unfavorable displacement                                                                         Results            __________________________________________________________________________    B1 Ex. 0.3Nb--0.08Ym      ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B2 Ex. 1.2Ta--0.09Ym      ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B3 Ex. 2.6Mo--0.1Ym       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B4 Ex. 2.5W--0.09Ym       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B5 Ex. 0.3Nb--0.9Ta--0.09Ym                                                                             ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B6 Ex. 0.3Nb--1.6Mo--0.07Ym                                                                             ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B7 Ex. 0.31Nb--1.3W--0.09Ym                                                                             ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B8 Ex. 1Ta--1Mo--0.1Ym    ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B9 Ex. 1Ta--1.4W--0.08Ym  ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B10                                                                              Ex. 1.6Mo--1.1W--0.08Ym                                                                              ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B11                                                                              Ex. 0.3Nb--1Mo--1W--0.08Ym                                                                           ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B12                                                                              Ex. 0.3Nb--0.8Ta--1W--0.07Ym                                                                         ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B13                                                                              Ex. 0.3Nb--0.7Ta--1.1Mo--0.08Ym                                                                      ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B14                                                                              Ex. 1Ta--1Mo--1W--0.07Ym                                                                             ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B15                                                                              Ex. 0.2Nb--0.7Ta--1.1Mo--1.1W--0.08Ym                                                                ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B16                                                                              Ex. 0.3Nb--0.05Ym      ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B17                                                                              Ex. 0.3Nb--1.5Mo--0.05Ym                                                                             ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B18                                                                              Ex. 0.3Nb--1Mo--0.05Ym ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      B19                                                                              Comp.                                                                             0.08Ln             X   X   ◯                                                                       Displaced after 550                                                                              Xycles                Ex.                                                                        B20                                                                              Comp.                                                                             0.107Ln--0.05Ti    X   X   ◯                                                                       Displaced after 740                                                                              Xycles                Ex.                                                                        B21                                                                              Comp.                                                                             0.9Mo--0.08Ym      X   X   ◯                                                                       Displaced after 870                                                                              Xycles                Ex.                                                                        B22                                                                              Comp.                                                                             0.4Ta--0.07Ym      ◯                                                                     X   ◯                                                                       Displaced after 650                                                                              Xycles                Ex.                                                                        __________________________________________________________________________

Example 3

The chemical ingredients of the heat-resistant stainless steelsaccording to the present invention and comparative materials are givenin Table 5. All the materials are based on 20Cr-5Al, and the steelsaccording to the examples of the present invention (C1 to C3) comprisethe 20Cr-5Al and, added thereto, Y for the purpose of ensuring theoxidation resistance and Ti and Nb in combination for the purpose ofenhancing the high-temperature proof stress. The comparative materials(C4 to C7) comprise 20Cr-5Al alone with no strengthening element addedor 20Cr-5Al with, added thereto, Ti or the like.

The procedure of Example 1 was repeated to prepare foil materials andmetallic carriers that were then subjected to the measurement of thehigh-temperature proof stress, evaluation of the oxidation resistanceand engine bench test in the same manner as that of Example 1. In thiscase, all the steels according to the examples of the present inventionhad a good hot workability and a good toughness in the form of ahot-rolled sheet. The results are summarized in Table 6. As is apparentfrom Table 6, the metallic carriers using the comparative foil materialshaving low proof stresses at 600° C. and 700° C. could not withstand the1200-cycle high-temperature thermal shock durability test, whereas allthe metallic carriers using the foil materials having high proofstresses at 600° C. and 700° C. and a good oxidation resistance gaverise to no unfavorable displacement even after the 1200-cycle thermalshock durability test and passed the high-temperature thermal shockdurability test. That is, the metallic carriers using the foil materialshaving enhanced proof stresses at 600° C. and 700° C. were excellent inthe structural durability of the honeycomb.

Further, in the metallic carriers according to the examples of thepresent invention, the occurrence of abnormal oxidation was not observedeven after the durability test, and the Al consumption of the foil wasas low as about 2%, which demonstrates that these carriers have also agood oxidation resistance.

                                      TABLE 5                                     __________________________________________________________________________    (wt. %)                                                                       Mark      C   N    C + N                                                                              Cr  Al  Ti  Nb   Y   Others                           __________________________________________________________________________    Ex.  C1   0.006                                                                             0.0065                                                                             0.0125                                                                             20.00                                                                             5.16                                                                              0.034                                                                             0.15 0.081                                                                             --                               Ex.  C2   0.005                                                                             0.0068                                                                             0.0118                                                                             20.11                                                                             5.21                                                                              0.032                                                                             0.30 0.074                                                                             --                               Ex.  C3   0.005                                                                             0.0060                                                                             0.0110                                                                             19.72                                                                             4.99                                                                              0.041                                                                             0.51 0.079                                                                             --                               Comp.                                                                              C4   0.007                                                                             0.0049                                                                             0.0119                                                                             20.10                                                                             5.28                                                                              --* --*  --* Ln = 0.08*                       Ex.                                                                           Comp.                                                                              C5   0.008                                                                             0.0060                                                                             0.0140                                                                             20.34                                                                             5.24                                                                              0.05                                                                              --*  --* Ln = 0.107*                      Ex.                                                                           Comp.                                                                              C6   0.007                                                                             0.0060                                                                             0.0130                                                                             20.41                                                                             5.32                                                                              0.01*                                                                              0.05*                                                                             0.080                                                                             --                               Ex.                                                                           Comp.                                                                              C7   0.014                                                                             0.0052                                                                             0.0192                                                                             20.7                                                                              5.20                                                                              0.01*                                                                              0.11*                                                                             0.071                                                                             --                               Ex.                                                                           __________________________________________________________________________     Note) *: Outside the scope of the invention                              

                                      TABLE 6                                     __________________________________________________________________________    Classification                                                                         Main ingredients                                                                           High-temp.                                              of foil  other than Cr and                                                                          proof stress                                                                            Oxidation                                                                            Results of engine bench durability                                            test                                   materials                                                                              Al in foil material                                                                        600° C.                                                                     700° C.                                                                     resistance                                                                           Unfavorable displacement                                                                         Results             __________________________________________________________________________    C1  Ex.  0.03Ti--0.15Nb--0.08Y                                                                      ◯                                                                      ◯                                                                      ◯                                                                        Not displaced even after 1200                                                 cycles             ◯       C2  Ex.  0.03Ti--0.3Nb--0.07Y                                                                       ◯                                                                      ◯                                                                      ◯                                                                        Not displaced even after 1200                                                 cycles             ◯       C3  Ex.  0.04Ti--0.5Nb--0.08Y                                                                       ◯                                                                      ◯                                                                      ◯                                                                        Not displaced even after 1200                                                 cycles             ◯       C4  Comp.                                                                              0.08Ln       X    X    ◯                                                                        Displaced after 550                                                                              Xycles                  Ex.                                                                       C5  Comp.                                                                              0.107Ln--0.05Ti                                                                            X    X    ◯                                                                        Displaced after 740                                                                              Xycles                  Ex.                                                                       C6  Comp.                                                                              0.01Ti--0.05Nb--0.08Y                                                                      X    X    ◯                                                                        Displaced after 800                                                                              Xycles                  Ex.                                                                       C7  Comp.                                                                              0.01Ti--0.11Nb--0.07Y                                                                      ◯                                                                      X    ◯                                                                        Displaced after 600                                                                              Xycles                  Ex.                                                                       __________________________________________________________________________

Example 4

The chemical ingredients of the heat-resistant stainless steelsaccording to the present invention and comparative materials are givenin Table 7. All the materials are based on 20Cr-5Al, and the steelsaccording to the examples of the present invention (D1 to D3) comprisethe 20Cr-5Al and, added thereto, Ym for the purpose of ensuring theoxidation resistance and Ti and Nb in combination for the purpose ofenhancing the high-temperature proof stress. The comparative materials(D4 to D7) comprise the 20Cr-5Al alone with no strengthening elementadded or the 20Cr-5Al with, added thereto, Ti or the like.

The procedure of Example 1 was repeated to prepare foil materials andmetallic carriers that were then subjected to the measurement of thehigh-temperature proof stress, evaluation of the oxidation resistanceand engine bench test in the same manner as that of Example 1. In thiscase, all the steels according to the examples of the present inventionhad a good hot workability and a good toughness in the form of ahot-rolled sheet. The results are summarized in Table 8. As is apparentfrom Table 8, the metallic carriers using the comparative foil materialshaving low proof stresses at 600° C. and 700° C. could not withstand the1,200-cycle high-temperature thermal shock durability test, whereas allthe metallic carriers using the foil materials having high proofstresses at 600° C. and 700° C. and a good oxidation resistance gaverise to no unfavorable displacement even after the 1,200-cycle thermalshock durability test and passed the high-temperature thermal shockdurability test. That is, the metallic carriers using the foil materialshaving enhanced proof stresses at 600° C. and 700° C. were excellent inthe structural durability of the honeycomb. Further, in the metalliccarriers according to the examples of the present invention, theoccurrence of abnormal oxidation was not observed also after thedurability test, and the Al consumption of the foil was as low as about2%, which demonstrates that these carriers have also a good oxidationresistance.

                                      TABLE 7                                     __________________________________________________________________________    (wt. %)                                                                       Mark      C   N    C + N                                                                              Cr  Al  Ti   Nb   Ym  Others                          __________________________________________________________________________    Ex.  D1   0.007                                                                             0.0082                                                                             0.0152                                                                             20.01                                                                             5.16                                                                              0.032                                                                              0.16 0.080                                                                             --                              Ex.  D2   0.006                                                                             0.0071                                                                             0.0131                                                                             20.11                                                                             5.22                                                                              0.034                                                                              0.31 0.079                                                                             --                              Ex.  D3   0.008                                                                             0.0079                                                                             0.0159                                                                             19.79                                                                             5.01                                                                              0.041                                                                              0.49 0.101                                                                             --                              Comp.                                                                              D4   0.007                                                                             0.0049                                                                             0.0119                                                                             20.10                                                                             5.28                                                                              --*  --*  --* Ln = 0.08*                      Ex.                                                                           Comp.                                                                              D5   0.008                                                                             0.0060                                                                             0.0140                                                                             20.34                                                                             5.24                                                                              0.05 --*  --* Ln = 0.107*                     Ex.                                                                           Comp.                                                                              D6   0.006                                                                             0.0071                                                                             0.0131                                                                             20.09                                                                             5.14                                                                               0.015*                                                                             0.06*                                                                             0.091                                                                             --                              Ex.                                                                           Comp.                                                                              D7   0.014                                                                             0.0052                                                                             0.0192                                                                             20.5                                                                              5.19                                                                              0.01*                                                                               0.11*                                                                             0.09                                                                              --                              Ex.                                                                           __________________________________________________________________________     Note) *: Outside the scope of the invention                              

                                      TABLE 8                                     __________________________________________________________________________    Classification                                                                         Main ingredients                                                                            High-temp.                                             of foil  other than Cr and Al                                                                        proof stress                                                                            Oxidation                                                                           Results of engine bench durability                                            test                                   materials                                                                              in foil material                                                                            600° C.                                                                     700° C.                                                                     resistance                                                                          Unfavorable displacement                                                                         Results             __________________________________________________________________________    D1  Ex.  0.03Ti--0.16Nb--0.08Ym                                                                      ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       D2  Ex.  0.03Ti--0.3Nb--0.08Ym                                                                       ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       D3  Ex.  0.04Ti--0.5Nb--0.1Ym                                                                        ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       D4  Comp.                                                                              0.08Ln        X    X    ◯                                                                       Displaced after 550                                                                              Xycles                  Ex.                                                                       D5  Comp.                                                                              0.107Ln--0.05Ti                                                                             X    X    ◯                                                                       Displaced after 740                                                                              Xycles                  Ex.                                                                       D6  Comp.                                                                              0.015Ti--0.06Nb--0.09Ym                                                                     X    X    ◯                                                                       Displaced after 820                                                                              Xycles                  Ex.                                                                       D7  Comp.                                                                              0.01Ti--0.11Nb--0.09Ym                                                                      ◯                                                                      X    ◯                                                                       Displaced after 600                                                                              Xycles                  Ex.                                                                       __________________________________________________________________________

Example 5

The chemical ingredients of the heat-resistant stainless steelsaccording to the present invention and comparative materials are givenin Table 9. All the materials are based on 20Cr-5Al, and the steelsaccording to the examples of the present invention (E1 to E20) comprisethe 20Cr-5Al with, added thereto, Ln for the purpose of ensuring theoxidation resistance and Nb, Ta, Mo and W, either alone (exclusive ofNb) or in combination, for the purpose of enhancing the high-temperatureproof stress. The comparative materials (E21 to E24) comprise the20Cr-5Al alone with no strengthening element added or the 20Cr-5Al with,added thereto, Ti or the like.

The procedure of Example 1 was repeated to prepare foil materials andmetallic carriers that were then subjected to the measurement of thehigh-temperature proof stress, evaluation of the oxidation resistanceand engine bench test in the same manner as that of Example 1. In thiscase, all the steels according to the examples of the present inventionhad a good hot workability and a good toughness in the form of ahot-rolled sheet. The results are summarized in Table 10. As is apparentfrom Table 10, the metallic carriers using the comparative foilmaterials having low proof stresses at 600° C. and 700° C. could notwithstand the 1200-cycle high-temperature thermal shock durability test,whereas all the metallic carriers using the foil materials having highproof stresses at 600° C. and 700° C. and a good oxidation resistancegave rise to no unfavorable displacement even after the 1200-cyclethermal shock durability test and passed the high-temperature thermalshock durability test. That is, the metallic carriers using the foilmaterials having enhanced proof stresses at 600° C. and 700° C. wereexcellent in the structural durability of the honeycomb. Further, in themetallic carriers according to the examples of the present invention,the occurrence of abnormal oxidation was not observed even after thedurability test, and the Al consumption of the foil was as low as about2%, which demonstrates that these carriers have also a good oxidationresistance.

                                      TABLE 9                                     __________________________________________________________________________    (wt. %)                                                                       Mark    C  N   C + N                                                                             Cr Al Nb Ta  Nb + Ta                                                                            Mo W  Mo + W                                                                             Ln La P  Others               __________________________________________________________________________    Ex. E1  0.007                                                                            0.0057                                                                            0.0127                                                                            19.2                                                                             5.21                                                                             -- 1.11                                                                              1.11 -- -- --   0.091                                                                            -- 0.026                                                                            --                   Ex. E2  0.010                                                                            0.0085                                                                            0.0185                                                                            19.9                                                                             4.92                                                                             -- --  --   2.60                                                                             -- 2.60 0.073                                                                            -- 0.042                                                                            --                   Ex. E3  0.011                                                                            0.0071                                                                            0.0181                                                                            20.5                                                                             5.31                                                                             -- --  --   -- 2.50                                                                             2.50 0.086                                                                            -- 0.036                                                                            --                   Ex. E4  0.007                                                                            0.0084                                                                            0.0154                                                                            20.3                                                                             5.21                                                                             0.31                                                                             0.71                                                                              1.02 -- -- --   0.078                                                                            -- 0.027                                                                            --                   Ex. E5  0.009                                                                            0.0055                                                                            0.0145                                                                            21.0                                                                             5.00                                                                             0.30                                                                             --  0.30 1.50                                                                             -- 1.50 0.087                                                                            -- 0.018                                                                            --                   Ex. E6  0.008                                                                            0.0064                                                                            0.0144                                                                            19.5                                                                             5.34                                                                             0.31                                                                             --  0.31 -- 1.23                                                                             1.23 0.080                                                                            -- 0.030                                                                            --                   Ex. E7  0.006                                                                            0.0044                                                                            0.0104                                                                            19.8                                                                             5.29                                                                             -- 0.99                                                                              0.99 1.11                                                                             -- 1.11 0.069                                                                            -- 0.025                                                                            --                   Ex. E8  0.008                                                                            0.0099                                                                            0.0179                                                                            21.0                                                                             4.98                                                                             -- 1.01                                                                              1.01 -- 1.48                                                                             1.48 0.071                                                                            -- 0.026                                                                            --                   Ex. E9  0.010                                                                            0.0084                                                                            0.0184                                                                            21.9                                                                             5.03                                                                             -- --  --   1.50                                                                             1.08                                                                             2.58 0.071                                                                            -- 0.031                                                                            --                   Ex. E10 0.009                                                                            0.0084                                                                            0.0174                                                                            20.1                                                                             5.14                                                                             0.29                                                                             --  0.29 1.11                                                                             1.30                                                                             2.41 0.093                                                                            -- 0.018                                                                            --                   Ex. E11 0.007                                                                            0.0077                                                                            0.0147                                                                            19.2                                                                             5.31                                                                             0.30                                                                             0.61                                                                              0.91 -- 1.10                                                                             1.10 0.083                                                                            -- 0.031                                                                            --                   Ex. E12 0.011                                                                            0.0055                                                                            0.0165                                                                            20.3                                                                             5.20                                                                             0.31                                                                             0.62                                                                              0.93 1.01                                                                             -- 1.01 0.086                                                                            -- 0.031                                                                            --                   Ex. E13 0.007                                                                            0.0054                                                                            0.0124                                                                            20.3                                                                             5.19                                                                             -- 0.71                                                                              0.71 1.10                                                                             1.05                                                                             2.15 0.083                                                                            -- 0.019                                                                            --                   Ex. E14 0.006                                                                            0.0088                                                                            0.0148                                                                            21.2                                                                             5.09                                                                             0.30                                                                             0.55                                                                              0.85 1.02                                                                             1.15                                                                             2.17 0.110                                                                            -- 0.025                                                                            --                   Ex. E15 0.009                                                                            0.0048                                                                            0.0138                                                                            20.1                                                                             5.11                                                                             0.32                                                                             --  0.32 -- -- --   0.091                                                                            -- 0.034                                                                            --                   Ex. E16 0.007                                                                            0.0046                                                                            0.0116                                                                            19.3                                                                             5.18                                                                             0.51                                                                             --  0.51 1.44                                                                             -- 1.44 0.095                                                                            -- 0.036                                                                            --                   Ex. E17 0.010                                                                            0.0064                                                                            0.0164                                                                            20.8                                                                             5.24                                                                             0.80                                                                             --  0.80 1.09                                                                             -- 1.09 0.085                                                                            -- 0.031                                                                            --                   Ex. E18 0.008                                                                            0.0045                                                                            0.0125                                                                            20.09                                                                            5.31                                                                             0.31                                                                             --  0.31 -- -- --   -- 0.08                                                                             0.031                                                                            --                   Ex. E19 0.009                                                                            0.0077                                                                            0.0167                                                                            21.05                                                                            5.20                                                                             0.29                                                                             --  0.29 1.51                                                                             -- 1.51 -- 0.07                                                                             0.035                                                                            --                   Ex. E20 0.007                                                                            0.0081                                                                            0.0151                                                                            19.98                                                                            5.12                                                                             0.28                                                                             --  0.28 1.09                                                                             -- 1.09 -- 0.11                                                                             0.018                                                                            --                   Comp.                                                                             E21 0.007                                                                            0.0049                                                                            0.0119                                                                            20.10                                                                            5.28                                                                              --*                                                                              --*                                                                               --*  --*                                                                              --*                                                                              --* 0.08                                                                             -- 0.018                                                                            --                   Ex.                                                                           Comp.                                                                             E22 0.008                                                                            0.0060                                                                            0.0140                                                                            20.34                                                                            5.24                                                                              --*                                                                              --*                                                                               --*  --*                                                                              --*                                                                              --* 0.107                                                                            -- 0.019                                                                            Ti = 0.05*           Ex.                                                                           Comp.                                                                             E23 0.009                                                                            0.0054                                                                            0.0144                                                                            21.11                                                                            5.27                                                                             -- --  --   0.9*                                                                             -- 0.9*  --*                                                                             -- --*                                                                              Y = 0.08*            Ex.                                                                           Comp.                                                                             E24 0.014                                                                            0.0053                                                                            0.0193                                                                            20.7                                                                             5.20                                                                             --  0.37*                                                                             0.37*                                                                             -- -- --   0.079                                                                            -- 0.032                                                                            --                   Ex.                                                                           __________________________________________________________________________     Note) *: Outside the scope of the invention                              

                                      TABLE 10                                    __________________________________________________________________________    Classification            High-temp.                                          of foil                                                                              Main ingredients other than                                                                      proof stress                                                                          Oxidation                                                                           Results of engine bench                                                       durability test                       materials                                                                            Cr and Al in foil material                                                                       600° C.                                                                    700° C.                                                                    resistance                                                                          Unfavorable displacement                                                                         Results            __________________________________________________________________________    E1 Ex. 1.1Ta--0.09Ln      ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E2 Ex. 2.6Mo--0.07Ln      ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E3 Ex. 2.5W--0.09Ln       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E4 Ex. 0.3Nb--0.7Ta--0.08Ln                                                                             ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E5 Ex. 0.3Nb--1.5Mo--0.09Ln                                                                             ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E6 Ex. 0.3Nb--1.2W--0.08Ln                                                                              ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E7 Ex. 1Ta--1.1Mo--0.07Ln ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E8 Ex. 1Ta--1.5W--0.07Ln  ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E9 Ex. 1.5Mo--1W--0.07Ln  ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E10                                                                              Ex. 0.3Nb--1.1Mo--1.3W--0.09Ln                                                                       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E11                                                                              Ex. 0.3Nb--0.6Ta--1.1W--0.08Ln                                                                       ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E12                                                                              Ex. 0.3Nb--0.6Ta--1Mo--0.09Ln                                                                        ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E13                                                                              Ex. 0.7Ta--1.1Mo--1W--0.08Ln                                                                         ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E14                                                                              Ex. 0.3Nb--0.6Ta--1Mo--1.1W--0.11Ln                                                                  ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E15                                                                              Ex. 0.3Nb--0.09Ln      ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E16                                                                              Ex. 0.5Nb--1.4Mo--0.1Ln                                                                              ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E17                                                                              Ex. 0.8Nb--1Mo--0.09Ln ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E18                                                                              Ex. 0.3Nb--0.08La      ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E19                                                                              Ex. 0.3Nb--1.5Mo--0.07La                                                                             ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E20                                                                              Ex. 0.3Nb--1Mo--0.1La  ◯                                                                     ◯                                                                     ◯                                                                       Not displaced even after 1200                                                 cycles             ◯      E21                                                                              Comp.                                                                             0.08Ln             X   X   ◯                                                                       Displaced after 550                                                                              Xycles                Ex.                                                                        E22                                                                              Comp.                                                                             0.107Ln--0.05Ti    X   X   ◯                                                                       Displaced after 740                                                                              Xycles                Ex.                                                                        E23                                                                              Comp.                                                                             0.08Y--0.9Mo       X   X   ◯                                                                       Displaced after 850                                                                              Xycles                Ex.                                                                        E24                                                                              Comp.                                                                             0.09Ln--0.4Ta      ◯                                                                     X   ◯                                                                       Displaced after 600                                                                              Xycles                Ex.                                                                        __________________________________________________________________________

Example 6

The chemical ingredients of the heat-resistant stainless steelsaccording to the present invention and comparative materials are givenin Table 11. All the materials are based on 20Cr-5Al, and the steelsaccording to the examples of the present invention (F1 to F6) comprisethe 20Cr-5Al with, added thereto, Ln for the purpose of ensuring theoxidation resistance and Ti and Nb in combination for the purpose ofenhancing the high-temperature proof stress. The comparative materials(F7 to F10) comprise the 20Cr-5Al alone with no strengthening elementadded or the 20Cr-5Al with, added thereto, Ti or the like.

The procedure of Example 1 was repeated to prepare foil materials andmetallic carriers that were then subjected to the measurement of thehigh-temperature proof stress, evaluation of the oxidation resistanceand engine bench test in the same manner as that of Example 1. In thiscase, all the steels according to the examples of the present inventionhad a good hot workability and a good toughness in the form of ahot-rolled sheet. The results are summarized in Table 12. As is apparentfrom Table 12, the metallic carriers using the comparative foilmaterials having low proof stresses at 600° C. and 700° C. could notwithstand the 1,200-cycle high- temperature thermal shock durabilitytest, whereas all the metallic carriers using the foil materials havinghigh proof stresses at 600° C. and 700° C. and a good oxidationresistance gave rise to no unfavorable displacement even after the1200-cycle thermal shock durability test and passed the high-temperaturethermal shock durability test. That is, the metallic carriers using thefoil materials having enhanced proof stresses at 600° C. and 700° C.were excellent in the structural durability of the honeycomb. Further,in the metallic carriers according to the examples of the presentinvention, the occurrence of abnormal oxidation was not observed evenafter the durability test, and the Al consumption of the foil was as lowas about 2%, which demonstrates that these carriers have also a goodoxidation resistance.

                                      TABLE 11                                    __________________________________________________________________________    (wt. %)                                                                       Mark      C   N    C + N                                                                              Cr  Al  Ti  Nb   Ln  La  P                            __________________________________________________________________________    Ex.  F1   0.005                                                                             0.0078                                                                             0.0128                                                                             20.19                                                                             5.19                                                                              0.031                                                                             0.16 0.081                                                                             --  0.031                        Ex.  F2   0.005                                                                             0.0060                                                                             0.0110                                                                             19.98                                                                             4.99                                                                              0.035                                                                             0.30 0.101                                                                             --  0.035                        Ex.  F3   0.006                                                                             0.0075                                                                             0.0135                                                                             20.00                                                                             5.16                                                                              0.040                                                                             0.51 0.079                                                                             --  0.029                        Ex.  F4   0.008                                                                             0.0084                                                                             0.0164                                                                             21.09                                                                             4.93                                                                              0.032                                                                             0.20 --  0.092                                                                             0.034                        Ex.  F5   0.007                                                                             0.0077                                                                             0.0147                                                                             20.05                                                                             5.20                                                                              0.031                                                                             0.28 --  0.073                                                                             0.031                        Ex.  F6   0.009                                                                             0.0048                                                                             0.0138                                                                             22.31                                                                             5.13                                                                              0.035                                                                             0.35 --  0.065                                                                             0.020                        Comp.                                                                              F7   0.007                                                                             0.0049                                                                             0.0119                                                                             20.10                                                                             5.28                                                                              --* --*  0.080                                                                             --  0.018                        Ex.                                                                           Comp.                                                                              F8   0.008                                                                             0.0060                                                                             0.0140                                                                             20.34                                                                             5.24                                                                              0.05                                                                              --*  0.107                                                                             --  0.015                        Ex.                                                                           Comp.                                                                              F9   0.008                                                                             0.0043                                                                             0.0123                                                                             21.35                                                                             5.13                                                                              --*  0.08*                                                                             0.089                                                                             --  0.030                        Ex.                                                                           Comp.                                                                              F10  0.014                                                                             0.0052                                                                             0.0192                                                                             20.5                                                                              5.18                                                                              0.01*                                                                              0.11*                                                                             0.09                                                                              --  0.032                        Ex.                                                                           __________________________________________________________________________     Note) *: Outside the scope of the invention                              

                                      TABLE 12                                    __________________________________________________________________________    Classification         High-temp.                                             of foil Main ingredients other than                                                                  proof stress                                                                            Oxidation                                                                           Results of engine bench durability                                            test                                   materials                                                                             Cr and Al in foil material                                                                   600° C.                                                                     700° C.                                                                     resistance                                                                          Unfavorable displacement                                                                         Results             __________________________________________________________________________    F1 Ex.  0.03Ti--0.16Nb--0.08Ln                                                                       ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       F2 Ex.  0.035Ti--0.3Nb--0.1Ln                                                                        ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       F3 Ex.  0.04Ti--0.5Nb--0.08Ln                                                                        ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       F4 Ex.  0.03Ti--0.2Nb--0.09La                                                                        ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       F5 Ex.  0.03Ti--0.3Nb--0.07La                                                                        ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       F6 Ex.  0.035Ti--0.35Nb--0.07La                                                                      ◯                                                                      ◯                                                                      ◯                                                                       Not displaced even after 1200                                                 cycles             ◯       F7 Comp.                                                                              0.08Ln         X    X    ◯                                                                       Displaced after 550                                                                              Xycles                 Ex.                                                                        F8 Comp.                                                                              0.107Ln--0.05Ti                                                                              X    X    ◯                                                                       Displaced after 740                                                                              Xycles                 Ex.                                                                        F9 Comp.                                                                              0.09Ln--0.08Nb X    X    ◯                                                                       Displaced after 800                                                                              Xycles                 Ex.                                                                        F10                                                                              Comp.                                                                              0.09Ln--0.11Nb ◯                                                                      X    ◯                                                                       Displaced after 600                                                                              Xycles                 Ex.                                                                        __________________________________________________________________________

INDUSTRIAL APPLICABILITY

As is apparent also from the Examples, the Fe-Cr-Al-base alloys used inthe present invention have a good hot workability, a good toughness inthe form of a hot-rolled sheet and, therefore, an excellent formabilityinto a foil or the like and are excellent in resistance to theoccurrence of abnormal oxidation, not to mention oxidation resistance,and excellent in thermal fatigue resistance by virtue of their excellenthigh-temperature proof stress, that is, can exhibit as a honeycombstructure excellent oxidation resistance and structural durability withrespect to the occurrence of troubles, such as change of shape, failure,etc., which is particularly worthy of attention.

Thus, the highly heat resistant metallic carrier for an automobilecatalyst according to the present invention has a highly heat-resistantproperty sufficient to withstand an engine thermal shock test whereinthe maximum temperature is 950° C.

Therefore, the present invention can provide an excellent metalliccarrier that can sufficiently cope with an increase in the temperatureof an automobile engine exhaust gas, which renders the present inventionvery useful from the viewpoint of industry.

We claim:
 1. A metallic carrier for an automobile catalyst, comprising ametallic honeycomb and a jacket, characterized in that said metallichoneycomb comprises a foil material comprising an Fe-Cr-Al-base alloyand having proof stresses of 22 kgf/mm² or more and 11 kgf/mm² or morerespectively at 600° C. and 700° C., the foil material being annealed ata temperature of the recrystallization temperature of the foil materialor above.
 2. The metallic carrier according to claim 1, wherein saidfoil material is a stainless steel foil material which comprises, interms of % by weight, more than 0.01 to 0.5% Y, 4.5 to 6.5% Al, 13 to25% Cr, 0.025% or less of C and 0.02% or less N, the total of C and Nbeing 0.03% or less, and, further, at least one member selected from thegroup consisting of (93.C/12+93.N/14)×1.1% to 3% Nb,(181.C/12+181.N/14)×1.5% to 3% Ta, 1 to 4% Mo and 1 to 4% W, the totalof Ta and Nb being 3% or less, the total of Mo and W being 4% or less,with the balance consisting of Fe and unavoidable impurities.
 3. Themetallic carrier according to claim 1, wherein said foil material is astainless steel foil material which comprises, in terms of % by weight,more than 0.01 to 0.5% Ym, said Ym comprising about 60% Y, about 35%heavy rare earth elements (Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) and about5% light rare earth elements (La, Ce, Pr, Nd, Pm, Sm and Eu), 4.5 to6.5% Al, 13 to 25% of Cr, 0.025% or less C and 0.02% or less of N, thetotal C and N being 0.03% or less, and, further, at least one memberselected from the group consisting of (93.C/12+93.N/14)×1.1% to 3% Nb,(181.C/12+181.N/14)×1.5% to 3% Ta, 1 to 4% Mo and 1 to 4% W, the totalof Ta and Nb being 3% or less, the total of Mo and W being 4% or less,with the balance consisting of Fe and unavoidable impurities.
 4. Themetallic carrier according to claim 1, wherein said foil material is astainless steel foil material which comprises, in terms of % by weight,more than 0.01 to 0.5% Y, 4.5 to 6.5% Al, 13 to 25% Cr, 0.025% or lessof C, 0.02% or less N, the total of C and N being 0.03% or less, 0.02%to (0.03+4.C+24.N/7) % Ti and more than (93.C/12+93.N/14) % to 2.0% Nb,with the balance consisting of Fe and unavoidable impurities.
 5. Themetallic carrier according to claim 1, wherein said foil material is astainless steel foil material which comprises, in terms of % by weight,more than 0.01 to 0.5% Ym, 4.5 to 6.5% Al, 13 to 25% Cr, 0.025% or lessof C, 0.02% or less N, the total of C and N being 0.03% or less, 0.02%to (0.03+4.C+24.N/7) % Ti and more than (93.C/12+93.N/14) % to 2.0% Nb,with the balance consisting of Fe and unavoidable impurities.
 6. Themetallic carrier according to claim 1, wherein said foil material is astainless steel foil material which comprises, in terms of % by weight,more than 0.06 to 0.15% Ln, said Ln being at least one element selectedfrom the group consisting of La, Pr, Ce and Nd, 8×(Ln+0.015)/45% to 0.1%P, 4.5 to 6.5% Al, 13 to 25% Cr, 0.025% or less C and 0.02% or less ofN, the total of C and N being 0.03% or less, and, further, at least onemember selected from the group consisting of (181.C/12+181.N/14)×1.5% to3% Ta, (93.C/12+93.N/14)×1.1% to 3% Nb, 1 to 4% Mo and 1 to 4% W, thetotal of Ta and Nb being 3% or less, the total of Mo and W being 4% orless, with the balance consisting of Fe and unavoidable impurities. 7.The metallic carrier according to claim 1, wherein said foil material isa stainless steel foil material which comprises, in terms of % byweight, more than 0.06 to 0.15% Ln, 8×(Ln+0.015)/45% to 0.1% P, 4.5 to6.5% Al, 13 to 25% Cr, 0.025% or less C, 0.02% or less of N, the totalof C and N being 0.03% or less, 0.02% to (0.03+4.C+24.N/7) % Ti and morethan (93.C/12+93.N/14) % to 2.0% Nb, with the balance consisting Fe andunavoidable impurities.